python全栈自学04——通过文件实现三级菜单增删改查
要求：文本文件中保存省市县三级菜单信息，通过文件实现对三级菜单的增删改查，并保存修改
这是菜单文本
{
"陕西省":{
"西安市":["未央区","灞桥区","长安区","雁塔区"],
"渭南市":["华县","潼关","大荔","白水"],
"宝鸡市":["岐山","凤翔","扶风","眉县"]
},
"四川省":{
"成都市":["锦江区","青羊区","金牛区","武侯区"],
"自贡市":["自流井区","贡井区","大安区","沿滩区"],
"泸州市":["江阳区","纳溪区","泸县","合江"]
},
"河南省":{
"洛阳市":["老城区","西工区","吉利区","郊区"],
"开封市":["龙亭区","鼓楼区","南关区","兰考县"],
"郑州市":["中原区","二七区","金水区","上街区"]
},
"青海省":{
"西宁市":["城东区","城西区","城北区","城中区"],
"海东":["平安","乐都","湟中","湟源"],
"玉树":["玉树","杂多","称多","治多"]
},
"辽宁省":{
"沈阳市":["和平区","沈河区","大东区","皇姑区"],
"大连市":["中山区","西岗区","瓦房店","旅顺口"],
"铁岭市":["银州区","清河区","西丰","开原"]
}
}代码如下：
f_read = open('3menu','r',encoding='utf-8') #打开文件
f_write = open('3menu1','w',encoding='utf-8') #创建菜单副本（不修改原文件）
dic = f_read.read() #读取文件，得到字符串格式
a = eval(dic) #将读到的文件对象f中的内容转换为字典格式（原本就是字典格式，从文件中读是字符串）
back_flag = False #返回上一级标志位
quit_flag = False #退出程序标志位
while not quit_flag or back_flag:
#进入第一级
for i in a:
print(i)
choice = input("1.增 2.删 3.改 4.退出菜单 or 输入省份进入下一级：")
if choice == "4":
quit_flag = True
break
elif choice in a:
#进入第二级
while not quit_flag or back_flag:
for j in a[choice]:
print(j)
choice2 = input("1.增 2.删 3.改 4.返回上级 5.退出菜单 or 输入城市进入下级：")
if choice2 == "4":
back_flag = True
break
elif choice2 == "5":
quit_flag = True
break
elif choice2 in a[choice]:
#进入第三级
while not quit_flag or back_flag:
for k in a[choice][choice2]:
print(k)
choice3 = input("已到达最后一级 1.增 2.删 3.改 4.返回上级 5.退出菜单")
if choice3 == "4":
back_flag = True
break
elif choice3 == "5":
quit_flag = True
break
elif choice3 == "1":
add_county = input("请输入添加的区县：")
a[choice][choice2].append(add_county)
elif choice3 == "2":
del_county = input("请输入要删除的区县：")
a[choice][choice2].remove(del_county)
elif choice3 == "3":
modify_county = input("请输入要修改的区县：")
modified_county = input("%s修改为：" % modify_county)
a[choice][choice2].remove(modify_county)
a[choice][choice2].append(modified_county)
else:
print("输入错误！")
elif choice2 == "1":
add_city = input("请输入添加的城市：")
a[choice][add_city] = []
elif choice2 == "2":
del_city = input("请输入要删除的城市：")
del a[choice][del_city]
elif choice2 == "3":
modify_city = input("请输入要修改的城市：")
modified_city = input("%s修改为：" % modify_city)
value = a[choice][modify_city]
del a[choice][modify_city]
a[choice][modified_city] = value
else:
print("输入错误！")
elif choice == "1":
add_province = input("请输入添加的省份：")
a[add_province] = {}
elif choice == "2":
del_province = input("请输入要删除的省份：")
del a[del_province]
elif choice == "3":
modify_province = input("请输入要修改的省份：")
modified_province = input("%s修改为：" % modify_province)
value = a[modify_province]
del a[modify_province]
a[modified_province] = value
else:
print("输入错误！")
b = str(a)
f_write.write(b)
f_read.close() #关闭文件
f_write.close()程序中还有大量重复的代码段，还需继续优化。